At conventions multiple suppliers provide multiple selections of products to multiple attendees and prospective users. Problems occur which interfere with efficient display and communications. One of these is the language barrier, particularly at international trade shows. Not all speak English and not all are fluent. Signs can be posted in several languages, but this is not as effective as a verbal message in the attendees native language. Another problem arises when the convention is heavily attended, and the attendee cannot get close to the booth to read or to converse. Another difficulty is that some attendees want only superficial information and others wish to get information in depth. A method of presorting and pre-selection of the audience is desirable, as provided in this invention. Short range radio transmission to local attendees has the disadvantage that neighboring booths or booths on parallel aisles will interact and interfere with one another. Museum display and automatic warehousing have similar problems. Interfering signals and noise interference are minimized by use of digital information transmission and modulation techniques.